1. Field of the Invention
The present invention relates to axial pin tumbler locks, and more particularly to an improved axial pin tumbler lock in which the tumblers are resettable to provide a large number of tumbler configurations that require separate operating keys, in order to permit the lock to be reset a large number of times to different operating configurations, on a periodic basis, if desired, so that the same operating key is usable for only a single combination of the lock tumblers, in order to prevent access to the area that is locked in the event an operating key is lost or is in the possession of an unauthorized person.
2. Description of the Related Art
Axial tumbler pin locks have been in use for some period of time, and a number of configurations of such locks have been disclosed. For example, in U.S. Pat. No. 3,541,819, which issued Nov. 24, 1970, to W. J. Kerr, an axial pin tumbler lock is disclosed in which a tumbler ball is included among and positioned between two of the generally cylindrical tumbler pins, in order to provide a lock structure that prevents tampering with the locks by unauthorized persons, and prevents unauthorized opening of the lock by the manipulation of a lock picking tool. However, the lock structure disclosed in that patent is operable by only a single key, and therefore if the key were to be lost or improperly acquired, the finder or acquirer of the key would be able to open the lock, and to obtain access to the area intended to be secured.
In order to minimize the risk of an unauthorized person having access to the area sought to be secured, a resettable axial tumbler pin lock was disclosed by D. J. Monahan in U.S. Pat. No. 3,422,646, which issued on Jan. 21, 1969. The lock disclosed in the Monahan patent includes a plurality of small, so-called wafers that are housed within a stationary annular body, and permit the tumblers to be reset so that a new operating key is required to open the lock. However, a limited number of resettable positions is available, and, additionally, the provision of a large number of very small wafers renders the lock very difficult to assemble and to repair, if necessary.
An improved form of a resettable axial tumbler pin lock is disclosed in U.S. Pat. No. Re. 28,319, which issued Jan. 28, 1975, to W. J. Kerr, and is based upon earlier-issued U.S. Pat. No. 3,756,049. In the Kerr reissue patent a lock structure is disclosed in which fewer parts are required that in the Monahan lock structure, but, again, only a limited number of tumbler combinations is available, specifically eight, and it is desirable that an even larger number of tumbler combinations be provided in order to reduce the likelihood that an unauthorized person in possession of an operating key will be able to open the lock when the tumbler pins are properly aligned to permit operation of the lock with such an operating key.
It is an object of the present invention to overcome the deficiencies of the prior art structures as hereinabove described, and to provide an improved axial pin tumbler lock structure in which a large number of different tumbler combinations can be provided, requiring a large number of different operating keys, in order to render unauthorized entry into the area locked by such a lock to be substantially less likely than would otherwise be the case. Summary of the Invention
Briefly stated, in accordance with one aspect of the present invention, an improved axial pin tumbler lock is provided that includes a tubular housing that has an axis and that includes an annular key opening to accept a tubular key having circumferentially spaced peripheral notches thereon. The annular key opening includes a radially outwardly extending notch and a radially inwardly extending notch. An inner cylindrical member defines the inner portion of the annular key opening, and is rotatably carried within the tubular housing. The housing also includes an inner annular sleeve non-rotatably carried by the housing at its innermost end, the sleeve having an internal bore adapted to rotatably receive the inner cylindrical member. The inner cylindrical member inlcudes a cylindrical inner end portion adapted to be rotatably received in the annular sleeve, and having a cylindrical outer portion that extends to the front part of the lock and defines the inner surface of the annular key opening. Positioned intermediate the inner and outer end portions of the inner cylindrical member is an annular stepped portion that extends radially outwardly from the axis to define a cylindrical intermediate portion that is supported within the tubular housing and is rotatable with respect thereto. First and second annular sleeves are rotatably carried on the outer end portion of the cylindrical inner body and are also rotatably received within the tubular housing. The first and second sleeves are in co-axial arrangement on the cylindrical inner body and are in contact with each other. Each of the first and second inner rotatable sleeves and the enlarged annular step portion of the cylindrical inner body includes a plurality of circumferentially disposed bores that extend in an axial direction relative to the axis of the cylindrical inner body, and that are capable of being placed into axial alignment with each other. The bores are disposed in a substantially circular array, and each bore is adapted to receive a plurality of cylindrical tumbler pins.
The inner cylindrical sleeve member also includes a plurality of axially extending bores disposed as a substantially circular array and capable of alignment with the bores in the first and second annular member and the stepped annular portion of the cylindrical inner body. The bores in the inner cylindrical sleeve member are blind bores and terminate inwardly of the axially spaced end faces of the sleeve.
The bores in each of the first and second sleeve members and the annular step portion each extend completely through the respective parts to permit tumbler pins to be shifted within the respective bores. The blind bores in the cylindrical sleeve member each include spring means that serve to urge the tumbler pins toward the front face of the lock housing.
The housing includes an inwardly extending circular flange positioned adjacent its outer face to engage at least a portion of an outer end of the outermost tumbler pins to limit outward axial movement of each of the axial groups of tumbler pins.
The interface between the stationary annular sleeve and the rotatable cylindrical member defines a locking plane. The interfaces between the annular stepped portion of the rotatable cylindrical member and the second rotatable sleeve member, as well as the interface between the first and second rotatable sleeve members each define respective reset planes. Each of the two reset planes is axially spaced from the other, and is also axially spaced from the locking plane.
The tumbler pin lengths are selected so that a first tubular reset key having external notches and engageable with the outermost ends of the outermost tumbler pins provides alignment of the tumbler ends to permit relative rotation of the second annular sleeve relative to the rotatable cylindrical inner body member to reset the tumblers to a plurality of first positions corresponding with the number of axial bores. The tumbler pins also permit a second tumbler reset key that provides alignment of the tumbler ends to permit relative rotation of the first and second inner annular sleeve members relative to each other in order to reset the tumblers to a plurality of second positons corresponding with the number of axial bores.